re PR c++/59123 ([c++11] can't forward-declare an object later defined constexpr)

/cp
2013-11-17  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/59123
	* decl.c (validate_constexpr_redeclaration): Redeclarations of
	variables can differ in constexpr.

/testsuite
2013-11-17  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/59123
	* g++.dg/cpp0x/constexpr-redeclaration1.C: New.
	* g++.dg/cpp0x/constexpr-decl.C: Adjust.

From-SVN: r204923

gcc/cp/ChangeLog

+2013-11-17  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/59123
+	* decl.c (validate_constexpr_redeclaration): Redeclarations of
+	variables can differ in constexpr.
+
 2013-11-16  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/29143

gcc/cp/decl.c

@@ -1216,10 +1216,12 @@ validate_constexpr_redeclaration (tree old_decl, tree new_decl)
       if (! DECL_TEMPLATE_SPECIALIZATION (old_decl)
 	  && DECL_TEMPLATE_SPECIALIZATION (new_decl))
 	return true;
+
+      error ("redeclaration %qD differs in %<constexpr%>", new_decl);
+      error ("from previous declaration %q+D", old_decl);
+      return false;
     }
-  error ("redeclaration %qD differs in %<constexpr%>", new_decl);
-  error ("from previous declaration %q+D", old_decl);
-  return false;
+  return true;
 }
 
 #define GNU_INLINE_P(fn) (DECL_DECLARED_INLINE_P (fn)			\

gcc/testsuite/ChangeLog

+2013-11-17  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/59123
+	* g++.dg/cpp0x/constexpr-redeclaration1.C: New.
+	* g++.dg/cpp0x/constexpr-decl.C: Adjust.
+
 2013-11-16  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/29143

gcc/testsuite/g++.dg/cpp0x/constexpr-decl.C

@@ -3,8 +3,7 @@
 
 struct S {
   static constexpr int size;	// { dg-error "must have an initializer" "must have" }
-  // { dg-error "previous declaration" "previous" { target *-*-* } 5 }
 };
 
 const int limit = 2 * S::size;
-constexpr int S::size = 256;	// { dg-error "" }
+constexpr int S::size = 256;

gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration1.C

+// PR c++/59123
+// { dg-do compile { target c++11 } }
+
+// Fwd-declarations
+struct S;
+extern const S s;
+
+// (... later) definitions
+struct S {};
+constexpr S s {};